The present invention relates to a transmission for a vehicle with propelling means, such as wheels or tracks, on each of the longitudinal sides thereof, said transmission comprising a right output shaft and a left output shaft coupled to the propelling means, a gear box with input and output shafts respectively coupled to a motor unit and to the right and left output shafts, a braking device which can reduce the rotational speed of the right and left output shafts and a steering unit comprising a shaft with, fitted thereon, a first and a second pinions, a third pinion engaged with the first pinion, and two planetary gear trains coaxial with the right and left output shafts, including each a planetary gear, a ring gear, planet wheels and a planet carrier and controlled by the second and third pinions for varying the rotational speeds of the right and left output shafts with respect to each other and thus changing the vehicle direction.
The planetary gear trains and the brakes in the transmissions of this type are located on either side of the gear box, in the vicinity of the longitudinal walls of the vehicles. In fact, because of their particular positioning within such transmissions, they make the motor-transmission coupling difficult and thus form an obstacle to an arrangement of the motor unit parallel to the right and left output shafts, which is a disadvantage for the manufacturers who generally have only a very confined space available to install the transmissions and motors in the vehicles.